Abstract

The room-temperature quality factors of silicon micromechanical oscillators have been investigated by scanning laser vibrometry. One of the flexural modes has very little attachment loss to its environment, which enables us to study internal loss mechanisms. After several consecutive annealing steps up to , the quality factor has increased from to . However, the decays to over six months in air. We conclude that near-surface lattice defects caused by reactive-ion etching and surfaceadsorbates are the main source of internal loss while surfaceadsorbates are responsible for the time dependence. We also discuss the thermoelastic limit in terms of Zener’s theory and flexural modal components of thin plates with vibratory volume change, and compare it with our results.

Received 15 March 2004Accepted 23 September 2004Published online 27 December 2004

Acknowledgments:

We thank B. Ilic and D. Czaplewski for sample fabrication at Cornell University. We also thank L. A. Kraus and M. H. Marcus for their contributions with the FEM. This work was supported by the Office of Naval Research and DARPA.